FUN with Matlab

I need a Matlab function that finds the last place in a line where a double character appears (that is, where the same character appears twice in a row)

So if the function is called locateDouble, locateDouble('adcdccd') should return 5 since inxes 5 is the first charcter of the last double character.
I posted my attempt at the program below, but it won't work.

function double=findDouble(line)
place=length(line);
while place>0;
for j=1:length(line)-1;
if j~==j+1
j=j+1
end
end
end

I need a Matlab function that finds the last place in a line where a double character appears (that is, where the same character appears twice in a row)

So if the function is called locateDouble, locateDouble('adcdccd') should return 5 since inxes 5 is the first charcter of the last double character.
I posted my attempt at the program below, but it won't work.

function double=findDouble(line)
place=length(line);
while place>0;
for j=1:length(line)-1;
if j~==j+1
j=j+1
end
end
end